TECHNICAL FIELD
[0001] The present invention relates to a living body information measuring apparatus for
measuring information of a living body such as blood pressure, heart beat and pulse
wave, and more particularly to a structure of a cuff for measuring blood pressure.
BACKGROUND ART
[0002] In the prior art, there is a known living body information measuring apparatus which,
for measurement, compresses a part such as wrist, upper arm, finger or ankle by using
a fluid bag supplied with a fluid such as air. A known blood pressure monitor uses
the oscillometric method to measure the blood pressure. In the oscillometric method,
a fluid bag is first wrapped around a tissue of a living body, and fixed. Then, either
while a pressure is applied to the tissue of the living body by feeding the fluid
into the fluid bag until the arteries of the tissue of the living body are completely
occluded, and thereafter the pressure of the fluid bag is gradually reduced at a constant
rate, or while the pressure of the fluid bad is increased by feeding the fluid thereinto
at a constant rate until the arteries of the tissue of the living body are completely
occluded, the method uses a sensor to detect a pulse wave signal of the arteries superimposed
on the pressure of the fluid bag, and measures systolic and diastolic blood pressures
thereof based on the amplitude variation of this signal by using a predetermined algorithm.
Thus, this method needs to compress the arteries at a predetermined pressure so as
to accurately detect a change in the arteries.
[0003] Now, multiple arteries are present in a living body part such as wrist, finger and
ankle. For example, two arteries, radial artery and ulnar artery, are present on the
palm side of the wrist, and three arteries are present in the ankle, while two arteries
and one artery are present on the palm side and on the dorsal side of a finger, respectively.
Further, various bones, muscles and tendons are present near these arteries and are
involved in the movement of the living body parts. For example, a long palmar muscle,
a flexor carpi radialis tendon, a flexor carpi ulnaris tendon, a flexor digitorum
superficialis tendon and a flexor digitorum profundus tendon are present on the palm
side of the wrist. Wrist bending is produced by the contraction of the long palmar
muscle and the flexor carpi radialis tendon. On the other hand, finger bending is
produced by the contraction of the flexor digitorum superficialis tendon and the flexor
digitorum profundus tendon. Thus, the living body parts have complex structures.
[0004] When a wrist or a finger is bent as described above, tendons present on the surface
of the wrist bulge, and the tendons become tense and tight. Therefore, if the above-described
method is used to measure blood pressure, the bulged tendons may, in some cases, hinder
the compression on the arteries as applied by the fluid bag, and there is a possibility
that contact intimacy between the fluid bag and the living body part may become poor.
Thus, there may be a case where the arteries cannot be occluded unless the pressure
of the fluid bag is set higher than a predetermined pressure, leading to a problem
that a reduction in the detectability of a pulse wave signal of the arteries is likely
to cause measurement errors.
[0005] Thus, as described e.g. in Japanese Patent (sic, correctly: Japanese Patent Publication)
2003-290156, a blood pressure monitor is proposed in which a cuff to compress the arteries is
formed by a plurality of fluid bags corresponding in number and positions to the respective
arteries, and in which these fluid bags are connected to each other, each having a
stacked structure in the direction of compressing the artery. FIG. 14 shows a cross-sectional
view in a state where the cuff of the blood pressure monitor compresses a wrist. Note
that only a wrist 5 and a cuff 2 are shown for convenience, omitting the showing of
a main body of the blood pressure monitor and others.
[0006] The wrist 5 is composed e.g. of a radial artery 10, an ulnar artery 11, and tendons
14 which are related to the movements of the wrist 5 and fingers. The cuff 2 has fluid
bags 101, 102 divided left and right with the tendons 14 therebetween, in which the
fluid bag 101 and the fluid bag 102 respectively compress the radial artery 10 and
the ulnar artery 11. The cuff 2 having such a structure can measure accurate living
body information because the respective fluid bags 101, 102 compress the radial artery
10 and the ulnar artery 11.
[0007] However, the compression force of the fluid bags 101, 102 to the tendons 14 is weak,
so that the bulge of the tendons 14 due to e.g. the bending of the wrist 5 may not
be suppressed in some cases. Therefore, if the tendons 14 bulge, the contact intimacy
between the cuff 2 and the wrist 5 becomes poor, so that the compression force to
the radial artery 10 and the ulnar artery 11 becomes weak. Thus, there may be a case
where the radial artery 10 and the ulnar artery 11 cannot be occluded, unless the
pressure of the fluid bags 101, 102 is set higher than a predetermined pressure. As
a result, this may cause measurement errors in some cases.
[0008] Further, if a user attaches the blood pressure monitor at a position shifted around
the wrist 5 from a predetermined position, the contact intimacy of the fluid bags
101, 102 with the radial artery 10 and the ulnar artery 11 becomes weak. This weakens
the compression force to the radial artery 10 and the ulnar artery 11, which may cause
measurement errors in some cases. In order to prevent this, a method is known in which
a hard clip board or the like is provided inside the cuff 2. However, this has a problem
that it is difficult for the user to attach it. Further, if the wrist or the fingers
are bent inward or bent outward, the intimate contact state of the fluid bags 101,
102 with the radial artery 10 and the ulnar artery 11 changes, thereby causing a change
in the compression state. Thus, it is required to provide a control jig for controlling
the postures of the wrist and fingers, reducing the portability of such blood pressure
monitor. In addition, in order to prevent the user from bending the wrist or fingers
inward, it is required to limit its posture for measurement, which may, in some cases,
force the user to perform measurements in an unnatural posture.
[0009] Further, as described in Japanese Patent (sic, correctly: Japanese Patent Publication)
2003-24286, a blood pressure monitor is proposed in which a cuff is formed of a fluid bag which
is not divided left and right. FIG. 15 shows a cross-sectional view in a state where
the cuff of the blood pressure monitor compresses a wrist. Note that only a wrist
5 and a cuff 2 are shown for convenience, omitting the showing of a main body of the
blood pressure monitor and others. The cuff 2 has a substantially circular-shaped
fluid bag 103 to cover the wrist 5. The fluid bag 103 compresses the wrist 5 regardless
of the presence of tendons 14.
[0010] The fluid bag 103 has a substantially circular-shaped cross section, so that it generally
has a property that its central portion expands most while an expansion of its side
portions is small. Thus, the compression force of the fluid bag 103 to the tendons
14 is strong to be able to suppress the bulge of the tendons 14 due to the bending
of the wrist or fingers. However, the contact intimacy of the fluid bag 103 with the
radial artery 10 and the ulnar artery 11 is weak, causing the compression force to
be weak, which may cause measurement errors in some cases.
DISCLOSURE OF INVENTION
[0011] An object of the present invention, to solve the problems described above, is to
provide a living body information measuring apparatus which can suppress the bulge
of tendons due to the bending of a wrist or fingers, and has good contact intimacy
with arteries, and which can make accurate measurements of living body information.
[0012] In order to achieve the above object, the present invention provides a living body
information measuring apparatus using a fluid bag to compress a living body and using
a sensor to detect a change in multiple arteries present in a tissue of the living
body for measuring living body information, wherein the fluid bag comprises: a compression
fluid bag which contacts the living body to measure the living body information from
the arteries, and which can be expanded and contracted by being supplied with a fluid;
and at least two independent auxiliary fluid bags which are provided on an outer side
of the compression fluid bag relative to the living body, and which can be expanded
and contracted by being supplied with the fluid, and wherein the auxiliary fluid bags
are respectively divided from each other.
[0013] According to such a structure, the compression fluid bag contacts the living body
to measure the living body information from the arteries, and the at least two auxiliary
fluid bags are respectively divided from each other, so that it can compress the respective
arteries. Thus, in such a tissue of the living body that a tight tissue such as tendons
is present at a substantially central portion with arteries on both sides thereof,
the compression fluid bag can compress the tendons and suppress the bulge of them,
so as to make it possible to make accurate measurements of the living body information.
[0014] According to the present invention, it is preferable in the improved invention described
above that the auxiliary fluid bags are respectively connected to each other via a
division portion having elasticity.
[0015] According to this structure, the auxiliary fluid bags can be prevented from separating
from each other, achieving good contact intimacy with the arteries. Thus, when the
fluid bag is wrapped around e.g. the wrist, it is not easy for the outside-positioned
auxiliary fluid bags to mutually separate due to a difference between the inner and
outer circumferences, thereby making it possible to make accurate measurements of
the living body information.
[0016] According to the present invention, it is preferable in the improved invention as
described that the auxiliary fluid bags are respectively divided at a substantial
center of the compression fluid bag around the living body.
[0017] According to this structure, in a tissue of the living body having a tight tissue
such as tendons positioned at the substantially central portion and having the arteries
positioned on both sides thereof, the auxiliary fluid bags have good contact intimacy
with the arteries, making it possible to make accurate measurements of the living
body information.
[0018] According to the present invention, it is preferable in the improved invention described
above that the auxiliary fluid bags cover a substantial center of the compression
fluid bag around the living body.
[0019] According to this structure, in a tissue of the living body having a tight tissue
such as tendons positioned at the substantially central portion and having the arteries
positioned on both sides thereof, the auxiliary fluid bags covering the substantial
center of the compression fluid bag can compress the tendons and suppress the bulge
of them, so that accurate measurements of the living body information can be made.
[0020] According to the present invention, it is preferable in the improved invention described
above that the auxiliary fluid bags include an auxiliary fluid bag covering the substantial
center of the compression fluid bag around the living body together with auxiliary
fluid bags positioned on both sides thereof, in which the number of layers of the
auxiliary fluid bag covering the substantial center of the compression fluid bag around
the living body is larger than the number of layers of the other auxiliary fluid bags.
[0021] According to this structure, in a tissue of the living body having a tight tissue
such as tendons positioned at the substantially central portion and having the arteries
positioned on both sides thereof, the auxiliary fluid bag with the larger number of
layers can compress the tendons so as to suppress the bulge of the tendons, so that
accurate measurements of the living body information can be made.
[0022] According to the present invention, it is preferable in the improved invention described
above that the auxiliary fluid bags include an auxiliary fluid bag covering the substantial
center of the compression fluid bag around the living body together with other auxiliary
fluid bags, in which the length of the auxiliary fluid bag covering the substantial
center of the compression fluid bag around the living body is longer than the length
of the other auxiliary fluid bags.
[0023] According to this structure, in a tissue of the living body having a tight tissue
such as tendons positioned at the substantially central portion and having the arteries
positioned on both sides thereof, the auxiliary fluid bag with the longer length can
compress the tendons so as to suppress the bulge of the tendons, so that accurate
measurements of the living body information can be made.
[0024] According to the present invention, it is preferable in the improved invention described
above that the sensor is a pressure sensor which is provided on an auxiliary fluid
bag different from an auxiliary fluid bag for allowing the fluid to flow thereinto.
[0025] According to this structure, noise at the time of allowing the fluid to flow into
the fluid bag is not easily transmitted to the pressure sensor, so that accurate measurements
of the living body information can be made.
BRIEF DESCRIPTION OF DRAWINGS
[0026]
FIG. 1 is an oblique view showing a state where a blood pressure monitor according
to an embodiment of the present invention is attached to a wrist;
FIG. 2 is a cross-sectional view showing a state where the blood pressure monitor
is attached to the wrist;
FIG. 3A is a cross-sectional view of a blood pressure monitor cuff of the blood pressure
monitor, while FIG. 3B is a cross-sectional view of FIG. 3A along line A-A';
FIG 4 is a cross-sectional view showing a state where the blood pressure cuff compresses
the wrist;
FIG 5A is a cross-sectional view of the blood pressure monitor cuff with a division
portion, while FIG 5B is a cross-sectional view of FIG 5A along ling B-B';
FIG. 6 is a cross-sectional view showing a state where the blood pressure cuff without
the division portion compresses a wrist;
FIG. 7 is a cross-sectional view showing a state where the blood pressure monitor
cuff with the division portion compresses the wrist;
FIG. 8 is a cross-sectional view showing a modified example of the blood pressure
monitor cuff;
FIG. 9 is a cross-sectional view showing a further modified example of the blood pressure
monitor cuff;
FIG 10 is a cross-sectional view showing a further modified example of the blood pressure
monitor cuff;
FIG. 11 is a cross-sectional view showing a further modified example of the blood
pressure monitor cuff;
FIG. 12 is a cross-sectional view showing a state where the blood pressure monitor
cuff compresses a wrist;
FIG. 13 is a cross-sectional view showing a state where a modified example of the
blood pressure monitor cuff compresses a wrist;
FIG. 14 is a cross-sectional view showing a state where a conventional blood pressure
monitor cuff compresses a wrist; and
FIG 15 is a cross-sectional view showing a state where a modified example of the conventional
blood pressure monitor cuff compresses a wrist.
BEST MODE FOR CARRAYING OUT THE INVENTION
[0027] Referring to FIG 1 and FIG 2, a blood pressure monitor (living body information measuring
apparatus) according to an embodiment embodying the present invention will be described.
FIG. 1 and FIG. 2 show a state where a blood pressure monitor 1 is attached to a wrist
5. The blood pressure monitor 1 comprises a blood pressure monitor main body 17 with
a built-in control unit of the blood pressure monitor 1, and a cuff belt 30 attached
to the wrist 5 for compressing arteries. Provided inside the blood pressure monitor
main body 17 are a pump 8 for allowing a fluid to flow in, a pressure sensor 13 for
detecting a pulse wave signal due to a change in the arteries, an outlet valve 12
for releasing the fluid, and so on which are connected via a tube 9 for supplying
and exhausting the fluid to and from the cuff belt 30.
[0028] The cuff belt 30 comprises: a band 6 for attaching the blood pressure monitor 1 to
the wrist 5; a hook-and-loop fastener 7; an elastic plate 3 for holding the attachment
of the blood pressure monitor 1 to the wrist 5; a cuff 2 for measuring blood pressure
by compressing the arteries; and an inner cloth 4 having high elasticity. The hook-and-loop
fastener 7 fixes the band 6 around the wrist 5. The cuff 2 holds the fluid fed from
the pump 8, and compresses the arteries of the wrist 5. Note that the detailed structure
of the cuff 2 will be described later. Besides, the cuff 2 is manufactured e.g. by
blow-molding, or by e.g. heat-fusing and joining, a sheet-shaped material made from
a flexible material such as polyurethane or silicone which has good responsiveness
to a pulse wave of the arteries.
[0029] The wrist 5 is composed e.g. of a radial bone 15 positioned on the thumb side, an
ulnar bone 16 positioned on the little finger side, a radial artery 10, an ulnar artery
11, and tendons 14 which are related to the movements of the wrist 5 and fingers.
The radial artery 10 is positioned near the radial bone 15, while the ulnar artery
11 is positioned near the ulnar bone 16. Generally, the radial artery 10 is positioned
closer to the surface of the wrist 5 than the ulnar artery 11. When the wrist 5 or
fingers are bent, the tendons 14 bulge and become tight.
[0030] Next, the operation of the blood pressure monitor 1 attached to the wrist 5 for measuring
blood pressure will be described. When the blood pressure measurement starts, the
pump 8 provided inside the blood pressure monitor 1 feeds a fluid to the cuff 2 to
compress the wrist 5. When the cuff 2 reaches a predetermined pressure, the pump 8
stops. Then, the fluid held in the cuff 2 is exhausted via the outlet valve 12 to
reduce the pressure of the cuff 2 at a constant rate. At this time, simultaneously,
a pulse wave signal (information of a living body) indicating a change in the arteries
of the radial artery 10 and the ulnar artery 11 is captured by the cuff 2, and is
converted by the pressure sensor 13, based on the amplitude of the pulse wave signal,
to pressure values, from which a systolic blood pressure and a diastolic blood pressure
are calculated using a predetermined algorithm.
[0031] Next, the structure of the cuff 2 will be described with reference to FIG 3 and FIG
4. FIG 4 shows a state where the cuff 2 compresses the wrist 5. In FIG 4, only the
cuff 2 and the wrist 5 are shown for convenience, omitting the showing of the blood
pressure monitor main body 17 and others. The cuff 2 is formed of: a compression fluid
bag 18 which is provided for detecting a pulse wave signal, and which can be expanded
and contracted by being supplied with a fluid; and two auxiliary fluid bags 19, 20
which are provided on an outer side of the compression fluid bag 18, and which can
be expanded and contracted by being supplied with the fluid. The auxiliary fluid bags
19, 20 have a two-layer structure, and are connected to the compression fluid bag
18 via opening portions 21. Further, the auxiliary fluid bags 19, 20 are respectively
divided from each other.
[0032] In the cuff 2 described above, the compression fluid bag 18 compresses the tendons
14, the radial artery 10 and the ulnar artery 11, while the auxiliary fluid bag 19
and the auxiliary fluid bag 20 compress the radial artery 10 and the ulnar artery
11, respectively. Thus, the bulge of the tendons due to the bending of the wrist 5
and fingers can be suppressed, so that the contact intimacy of the compression fluid
bag 18 and the auxiliary fluid bags 19, 20 with the wrist 5 is not hindered, making
it possible to make accurate measurements of living body information. Further, the
length of the compression fluid bag 18 is long to compress the tendons 14, the radial
artery 10 and the ulnar artery 11. Thus, even if the cuff 2 is attached at a position
shifted from a predetermined attachment position, it has good contact intimacy with
the radial artery 10 and the ulnar artery 11, making it possible to make accurate
measurements of living body information.
[0033] Referring next to FIG. 5 to FIG. 13, modified examples of the structures of cuffs
2 will be described. In FIG 6 to FIG. 10, FIG 12 and FIG. 13, only a cuff 2 and the
wrist 5 are shown for convenience, omitting the showing of the blood pressure monitor
main body 17 and others. First, a cuff 2 shown in FIG. 5 and FIG. 7 will be described.
FIG 6 shows a state where a cuff 2 formed of auxiliary fluid bags 19, 20 without a
division portion 22 attached thereto compresses the wrist 5. FIG. 7 shows a state
where the cuff 2 compresses the wrist 5. In the cuff 2, the auxiliary fluid bag 19
and the auxiliary fluid bag 20 are connected to each other via a division portion
22 having elasticity. The other structure is the same as the structure of FIG. 3 described
above.
[0034] The wrist 5 has a substantially circular-shaped cross section, so that when a cuff
2 is attached to the wrist 5, there occurs a difference between an inside length and
an outside length of the cuff 2. Thus, as shown in FIG 6, the auxiliary fluid bag
19 and the auxiliary fluid bag 20 may be expanded too much left and right, causing
their contact intimacy with the radial artery 10 and the ulnar artery 11 to be poor,
and also causing the direction of compressing the auxiliary fluid bag 19 and the auxiliary
fluid bag 20 to be shifted from a predetermined direction, so that in some cases it
may not be possible to properly compress the radial artery 10 and the ulnar artery
11. For this reason, the auxiliary fluid bags 19, 20 are provided with a division
portion 22, whereby even when the cuff 2 is attached to the wrist 5, it is possible
to compress the radial artery 10 and the ulnar artery 11 in a proper direction, thereby
making it possible to make accurate measurements of living body information.
[0035] Next, a cuff 2 shown in FIG. 8 will be described. In this cuff 2, an auxiliary fluid
bag 23 is provided between the auxiliary fluid bag 19 and the auxiliary fluid bag
20. The other structure is the same as the structure of FIG. 3 described above. When
this cuff 2 is attached to the wrist 5, the auxiliary fluid bag 23 compresses the
tendons 14 positioned at a substantially central portion of the wrist 5, making it
possible to suppress the bulge of the tendons 14, while at the same time the auxiliary
fluid bags 19, 20 can compress the radial artery 10 and the ulnar artery 11, so that
accurate measurements of living body information can be made.
[0036] Next, a cuff 2 shown in FIG. 9 will be described. In this cuff 2, an auxiliary fluid
bag 24 is provided between the auxiliary fluid bag 19 and the auxiliary fluid bag
20, in which the length L1 of the auxiliary fluid bag 24 is longer than the length
L2 of the auxiliary fluid bags 19, 20. The other structure is similar to the structure
of FIG. 8 described above. When this cuff 2 is attached to the wrist 5, the auxiliary
fluid bag 24 further compresses the tendons 14 positioned at the substantially central
portion of the wrist 5, making it possible to suppress the bulge of the tendons 14,
while at the same time the auxiliary fluid bags 19, 20 can compress the radial artery
10 and the ulnar artery 11, so that accurate measurements of living body information
can be made.
[0037] Next, a cuff 2 shown in FIG. 10 will be described. In this cuff 2, an auxiliary fluid
bag 25 is provided between the auxiliary fluid bag 19 and the auxiliary fluid bag
20, in which the number of layers of the auxiliary fluid bag 25 is larger than the
number of layers of the auxiliary fluid bags 19, 20. The other structure is similar
to the structure of FIG. 9 described above. When this cuff 2 is attached to the wrist
5, the auxiliary fluid bag 25 further compresses the tendons 14 positioned at the
substantially central portion of the wrist 5, making it possible to suppress the bulge
of the tendons 14, while at the same time the auxiliary fluid bags 19, 20 can compress
the radial artery 10 and the ulnar artery 11, so that accurate measurements of living
body information can be made.
[0038] Next, a cuff 2 shown in FIG. 11 and FIG. 12 will be described. In this cuff 2, the
length L12 of the auxiliary fluid bag 20 is made longer than the length L11 of the
auxiliary fluid bag 19, while the auxiliary fluid bag 20 has a predetermined length
to cover at least a substantial center of the wrist 5. The other structure is similar
to the structure shown in FIG. 3 described above. When this cuff 2 is attached to
the wrist 5, the auxiliary fluid bag 20 compresses the tendons 14 positioned at the
substantially central portion of the wrist 5, making it possible to suppress the bulge
of the tendons 14, while at the same time the auxiliary fluid bags 19, 20 can compress
the radial artery 10 and the ulnar artery 11, so that accurate measurements of living
body information can be made.
[0039] Further, the ulnar artery 11 is located deeper from the surface of the wrist 5 than
the radial artery 10, while the cross-sectional area of the radial bone 15 is larger
than the cross-sectional area of the ulnar bone 16, so that the wrist 5 may not be
left-right symmetrical at the substantially central portion in some cases. Thus, it
may not always be suitable for the auxiliary fluid bags 19, 20 to be left-right symmetrical
at the substantially central portion of the cuff 2. Since the auxiliary fluid bag
20 has a predetermined length to cover at least the substantial center of the wrist
5, it can assist the force to compress the tendons 14, and can compress the ulnar
artery 11, making it possible to make accurate measurements of living body information
for a left-right unsymmetrical living body part.
[0040] Next, a cuff 2 shown in FIG. 13 will be described. In this cuff 2, a pressure sensor
27 is provided on the auxiliary fluid bag 19, while a pump 26 is provided on the auxiliary
fluid bag 20 for allowing a fluid to flow thereinto. The other structure is similar
to the structure shown in FIG. 12 described above. The vibration of the pump 26 must
go through the auxiliary fluid bag 20 and the compression fluid bag 18 before being
transmitted to the pressure sensor 27, so that the vibration of the pump 26 is not
easily transmitted to the pressure sensor 27, making it possible to make accurate
measurements. Note that noise can be further reduced if the size of an inlet hole
29 to allow the fluid to flow in is smaller than a connecting portion 28 between the
pressure sensor 27 and the auxiliary fluid bag 19.
[0041] In the blood pressure monitor 1 of the embodiment described above, the cuff 2 can
suppress the bulge of the tendons 14, so that it is not easy for a user to bend the
wrist or fingers inward or outward. Thus, it is not necessary to provide the cuff
2 with a control jig for controlling the postures of the wrist and fingers when measuring
the blood pressure, and it is not necessary to limit the posture of the user for measurement,
making it easier for the user to use it. In addition, the compression fluid bag 18
is not divided left and right, so that it can adapt to the shift of the attachment
position of the cuff 2 and to variations in structure e.g. of the wrist of the user.
This makes it possible to make accurate measurements of living body information, and
makes it easier for the user to it.
[0042] Note that that the present invention is not limited to the structures of the embodiments
described above, and various modifications are possible within the scope which does
not change the spirit the present invention. For example, although the pressure sensor
27 has been used as a sensor to measure blood pressure, it is not limited thereto
and can be any sensor which can detect a change in the arteries. In addition, the
embodiments described above has shown an example in the case where the blood pressure
monitor is attached to the wrist 5, but it is not limited thereto, and can be attached
to another such as finger, ankle, upper arm and neck as well.
[0043] This application is based on Japanese patent application
2005-337571, the content of which is to be consequently incorporated into the present invention
by reference to the specification and drawings of the above-described patent application.
[0044] The present invention has been sufficiently described using presently preferred embodiments
with reference to the attached drawings, but it may be obvious to those ordinarily
skilled in the art that various alterations and modifications are possible. Accordingly,
such alterations and modifications do not depart from the scope of the present invention,
and should be interpreted to be included within the scope of the present invention.